In a known technique, a removable memory device such as a semiconductor memory is mounted to an information processing apparatus that is an external apparatus of the memory device, and a predetermined function is implemented in the information processing apparatus by using information such as a software program or data that is stored in the memory device.
This type of a memory device may sometimes be provided with a security function for ensuring the confidentiality of the information stored in the memory device. For example, Patent Document 1 discloses a method in which data outputted from a storage part is encrypted by using key data. The Patent Document 1 proposes a technique of additionally providing an encryption circuit in the semiconductor memory to thereby apply more complicated encryption to a signal outputted from the semiconductor memory.